The present invention relates to a metal gasket and in particular to a metal gasket suitable for use for a flange made of synthetic resin.
Heretofore a flange used in an inlet system of an engine has been made in general of aluminium. However, recently, there is a tendency that synthetic resin obtained e.g. by reinforcing 6-nylon with glass fiber is used therefor.
This is because it is possible to intend further weight and cost reduction owing to this material change.
However, in case where synthetic resin is used for a flange, there are a number of conditions, that it has a low rigidify, that it has a large thermal strain (deformation when it is heated), that deformation due to external force is great, etc., under which it is difficult to secure the sealing property as a gasket, compared with the case where the flange is made of aluminium.
The major part of gaskets used for such flanges made of synthetic resin are products made of rubber, e.g. rubber O-rings. This is because a large amount of compression and resilience can be obtained thereby by a small load.
FIG. 10 shows an example of construction, in which a rubber product sealing member B is used between a resin flange 1 and an aluminium flange 2. A groove 1a, into which the rubber product sealing member B is inserted, is formed in the resin flange 1.
In case where the product made of rubber (rubber O-ring) is used as a gasket, since permanent strain remains due to influences of temperature or with the passage of time, there are problems that so-called buckling is great, that the sealing property is easily damaged by vibrating load, that reliability is low for long term use, etc. Since there is a trend that the guaranty term of vehicles is elongated (e.g. 100,000 km to 300,000 km), such lowering in reliability due to buckling should be suppressed.
Although it can be thought to change the rubber material from HNBR to fluorocarbon rubber, fluorosilicone rubber, etc., taking the worsening in the sealing property due to buckling into account, the sealing property is worsened at low temperatures, if fluorocarbon rubber is used, and further cost is considerably raised, if fluorosilicone rubber is used.
In addition, since the product made of rubber has no definite shape, it has another problem that mounting thereof on a flange takes much time, which raises mounting work cost.
The present invention has been made in order to solve the problems of a gasket made of rubber used for a resin flange and a main object thereof is to provide a metal gasket having a high reliability wherein an appropriate amount of compression and resilience is secured and buckling is suppressed so that it can be fit for long term use, owing to the fact that only the elastically deformable region is used in processes, in which beads are compressed, when a flange is secured by screwing, by using a structure, which can suppress compressing load on the beads to a low value.
In order to achieve the above object, the present invention is characterized in that a metal gasket used for a flange made of synthetic resin comprises at least one elastic metal plate, on which a bead is formed.